Electricity generated at power plants is transmitted by high-voltage transmission lines to electrical substations, then is delivered to end customers through electricity distribution networks. The high-voltage transmission lines are often interconnected with each other, forming electricity transmission networks (often referred as “power grids”). The electrical substations at the edge of the power grids transform electricity (from the power grids) from high voltages (e.g., 110 kV or higher) to intermediate voltages (e.g., 50 kV or less). The electricity distribution networks, including additional electrical substations, transformers, power lines, and meters, deliver electricity to end customers at lower voltage for consumption (e.g., 110 V and 220 V for North American households).
Electric vehicles can store electrical energy in batteries and use one or more electric motors for propulsion. An electric vehicle such as Nissan Leaf and plug-in hybrid electric vehicle (PHEV) such as Toyota Prius Plug-in Hybrid can recharge the batteries by connecting an on-car charger to a standard household power outlet, or by connecting to a special-purpose charging equipment installed at households or at public-accessible locations (e.g., parking garage, curb side, etc.). Examples of special-purpose charging equipment are Electric Vehicle Supply Equipment (EVSE) and charging stations.